also dragonborn arn't so much a race as they are a magically infused divine sect.
their basicly start leaning towards the mindset of whatever god rebirthed them without skiping a beat.
Replace Bahamut with Tiamat and you change them from protector to destroyer and things flow naturally with intuitive changes
While they aren't a breeding race, they are still considered their own race. They have a culture, specific shared beliefs and certain defining characteristics. They are merely changed into their current form by an exterior force.
And yes, you could change it to another protector/destroyer angle... but you're advocating Aasterinian, who takes the place of neither. Aasternian is more the heckler in the audience for the big fight.
meanwhile if I tried to say "monks are chaotic party animals" with a strait face I think you would either think I'm stupid or burst out laughing.
Or I'd point you towards the Drunken Master PrC.
(yes, it exists - Complete Warrior.)
So to me it's not so much changing a race then rewriting a narrative by changing one very small piece of text that is the vocal point of it.
Take the Cleric and, silly as its, replace its god with a gerbil go ahead and make it the holy gerbil of Antiark.
it's silly, heck yes, but many things are and they work; everything still lines up in the class and nothing gos amiss, even if its silly.
But the Cleric is written to allow for such things in most settings. Clerics can worship whatever they choose and still gain their power (usually others will say they are getting their power from something behind-the-scenes). I even played a monkey-man Cleric who worshiped his creator (the Sun God) as the Great Banana-God, He Who Made The Divine Banana!
But Dragonborn aren't designed with such a stipulation. They are specifically devoted to one single deity. It can be changed (as can all things), but a change to it will have significant consequences. Changing the deity to anything else, even if you keep the guardian-style they have, will alter their entire belief system and their divinely-mandated purpose.
I guess what I'm trying to say is this: be careful what you change. Think it through and what it means for the game world, rather than just your mechanical benefit. And perhaps consider that you are trying to do too much with this character. Sometimes you should just leave something out...
Especially when you could play up the nobility supposedly instilled in you by Bahamut warring with the conniving devil side and the demented demon side. 
